If you both are moving to a smaller new place and you are paying for it as well, she cannot push you out. Your name would be on the lease, correct? Too bad if that is not what she wants, you are paying for it. She can't take your children and leave you without some sort of court order.
She doesn't have standing to take your kids away. She will need something from the court on that. Contact a lawyer for some free initial consulting on this. Sounds like you may need to protect yourself.
